What is a seal coat?

A seal coat consists of sealing existing cracks in the pavement, adding a layer of asphalt binder, adding a layer of small rock, and covering the rock with an asphalt coat. This process usually happens in 3 steps as shown below.

  • Step 1: Seal the existing cracks in the pavement ("crack seal")
    • During this step, all small and large cracks in the existing pavement surface are routed and filled. Routing is the process of sawing a crack so that it is wide enough to fill with the sealing material. Generally, this process is completed in a few hours per block depending on the amount of cracking that needs to be sealed. Flaggers or other traffic control may be present during crack seal activities.
  • Step 2: Place asphalt and rock layers ("chip seal")
    • After the crack seal material has set up (generally a few weeks or months after crack sealing), the chip seal process is applied to the pavement surface. The chip seal consists of adding a layer of asphalt binder ("tack") to the pavement surface a few minutes ahead of adding a layer of small rock. The rock is then compacted with rollers following closely behind the seal coat operations. Flaggers and other traffic control will be present to direct traffic around the chip seal operations. Traffic may drive on the new surface immediately after rolling is completed.
    • Excess rock will be swept up with a street sweeper a day or two after the chip seal operations are complete.
  • Step 3: Cover rock with an asphalt coat ("fog seal")
    • The final step of a Seal Coat project is to add an asphalt coat called a "fog seal" to seal in any loose rocks to prevent them from coming loose. Prior to the fog seal being applied, the street will be swept again by a street sweeper to pick up any remaining loose rocks. The fog seal generally takes about 30 to 60 minutes to dry before traffic is allowed to drive on it.

Show All Answers

1. What is a seal coat?
2. Can I get in and out of my driveway while they are working?
3. Why does the city do seal coat projects?
4. How long do seal coats last before they need to be done again?
5. Why do seal coats when mill and overlays last longer?
6. Aren't seal coats messy, won't rocks get up in my yard or elsewhere on my property?
7. Will the loose rocks chip my windshield?
8. What types of streets are good candidates for seal coat projects?
9. How is parking affected by seal coat projects?